In conventional automatic glassware forming machines, hot ware such as bottles typically are set out in spaced relationship and in an upright orientation on a single line conveyor which transports the bottles to an annealing lehr. Occasionally two still-plastic bottles become stuck together and at other times bottles will fall down. Such stuck and fallen bottles interfere with proper operation of the lehr and cause jams at the stacker which pushes bottles off the conveyor into the lehr. Further, in machines where the bottles are sprayed with a protective coating prior to annealing, stuck and down bottles cause jams at the coating hood. It is thus desirable to remove stuck and down bottles from the conveyor and thus increase efficiency of operation.
Automatic detection and rejection of stuck and down bottles is generally known in the art, and non mechanical systems frequently employ photoelectric detectors. One example of such a rejection system is disclosed in U.S. Pat. No. 3,506,840 (Fink). In the Fink system, the angle of incidence of a radiation beam is adjusted such that radiation is reflected back to the sensor by down bottles. The sensor output controls a reject device. The reject device may be located downstream from the sensor, in which case a memory device responsive to the sensor output is provided to delay triggering of the reject device.
Although they do not relate to stuck or down bottle rejection, applicants are aware of the prior art rejection systems disclosed in U.S. Pat. Nos. 3,606,013 (Wideman); 3,716,136 (Birner et al); and 3,837,486 (Gardner). The Wideman system is adapted for use with glass containers which are transported suspended from support forks and comprises a photodetector system positioned at a predetermined elevation to detect bottles which are less than a predetermined minimum length. The light source is operated intermittently and operation thereof is synchronized with the line speed such that the detecting beam is generated at the time a bottle should be disposed in the path thereof. If the light path is not blocked, the sensor generates a control signal which is time-delayed by a signal delay device to actuate a reject mechanism located downstream from the inspection location.
Birner et al disclose a photoelectric inspection system for detecting misshapen containers in which a plurality of radiant energy beams are directed in predetermined relation to one another toward corresponding different, longitudinally spaced, portions of the formed containers. The output of various sensors positioned to detect portions of the beams are compared to determine whether the container portions are in proper relation to each other and to produce accept or reject control signals accordingly.
The Gardner system checks articles for proper shape or silhouette and utilizes a photoelectric detector to produce "diameter" pulses proportional in real time to the widths of articles being transported on a constant velocity conveyor. The diameter pulse is used to gate into a counter the output of a pulse generator synchronized with, and having a frequency proportional to, the speed of the conveyor. The counter count is then compared with predetermined maximum and minimum values and control signals for a downstream rejector device such as a conventional air nozzle are produced in dependence on the comparison. The reject control signal can be delayed for a predetermined period.
A principal disadvantage of prior art rejection systems is that they either require complex detection systems utilizing multiple radiation beams and sensors and/or require complex control logic and synchronization for controlling the detectors or analyzing the outputs produced thereby.